Diplomarbeit:

Ultrasound-based Measurement of Anatomical Structures

Bearbeiter: Jörg Jakobs
Aufgabensteller: Nassir Navab
Betreuer: Marco Feuerstein and Dr. Martin Haimerl (BrainLAB AG)

Abstract

Medical navigation systems support the surgeon at the planning and execution of surgeries. In orthopedics three dimensional representations of the involved bones are provided by navigation systems. Preoperative data sets allow a precise planning of the surgical procedure. During the surgery the surgeon is guided by the navigation system. The navigation system is able to show the planning data according to the current position of the patient in the operating room. For this purpose a registration establishing a relation between the plan and the intraoperative situation is necessary.

A development towards minimal invasive interventions can be observed in all areas of surgery. In general this means a minimization of cuts. At the same time, the access to relevant interior parts of the body is being reduced. To provide the surgeon with sufficient and precise information different solutions are developed depending on the respective application.

In orthopedics notably the visualization and measurement of bony structures is important. For this purpose ultrasound (US) may be used as a non-invasive and almost harmless imaging modality. Ultrasound images may be acquired during surgery and provide useful information about the position and orientation of bones.

At the start of the surgical procedure a registration between all involved data sets and tools is necessary. This thesis describes an workflow for the registration between ultrasound (US) and computed tomography (CT) data sets. Therefore a registration has to be found that produces the best correspondence between both data sets.

Some approaches of other authors try to compare the voxel information directly. The approach of this thesis is the detection of bony structures in the data sets. Then, these structures can be matched. A basis for the registration is the accurate measurement of the bones. Therefore it is necessary to detect bony structures in a precise and reproducible fashion.

The work starts with a systematic analysis of ultrasound images. A method for the preprocessing (artefact removal) of these images is tested. For the detection of bony structure a LiveWire^?-similar algorithm is developed. Another method will be described that is able to find the best position of a contour within an US image for a given preregistration. The mentioned algorithms are tested on several data sets of cadavers and a volunteer. Finally, the found structures will be matched with a surface model of the bone by an ICP algorithm to get a registration between US and CT data set.

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